In present-day communication systems it is known to transmit payload data, e.g. for the purpose of voice or video communication, both by means of what is referred to as circuit-switched technology and by way of packet-oriented networks. Communication systems which support both packet-oriented and circuit-switching transmission technologies are also referred to as “convergent” communication systems.
Based on the frequently used “Internet Protocol”, also referred to as IP for short, the term “Voice over IP”, abbreviated to VoIP, will also be used in the following description with reference to a packet-oriented transmission of payload data, for example voice data, the ITU-T standard (International Telecommunication Union-Telecommunications Standardization Sector) H.323 or the SIP (Session Initiation Protocol) protocol developed by the IETF (Internet Engineering Task Force) working group being widely established for VoIP communication.
A convergent communication system typically comprises at least one communication device by means of which a connection of both VoIP communication terminal devices and “traditional” communication terminal devices, i.e. terminal devices operating according to the circuit-switching principle, is made possible with the aid of appropriate interface modules. Interworking elements known as gateways are used for the purpose of converting between circuit-switched and packet-oriented transmission technologies. In this case a gateway performs a conversion between packet-oriented and circuit-switched transmission technologies and is often disposed between a packet-oriented network and a communication device operating according to a circuit-switching method. Here, the conversion relates both to signaling data and to payload data, i.e. in particular voice data, video data or also what is referred to as non-voice payload data such as, for example, tone signals of telecopying units or modems. “Payload” is the term used in technical circles for user information (useful) data. The gateways contain means for mutual conversion of data streams into suitable data packets. Digital signal processors, for example, are provided for converting payload data into digital information.
A problem occurring in convergent communication networks is an accumulation of multiple conversions between packet-oriented and circuit-switched transmission technologies which frequently has a negative impact on the voice quality on the communication units involved in the communication.
A method for direct media connection was proposed in the application with the application reference number 10354947.1 and the title “method for transmitting communication data in a communication system” filed with the German Patent and Trademark Office on Nov. 25, 2003, which method is characterized by a transmission of communication data via a direct media connection (DMC) without the involvement of a plurality of node units (gateways) and associated conversions necessary therewith.
The said method of a direct media connection for transmitting communication data in a communication system between a calling first communication unit and a called second communication unit initially provides a setup of a primary connection or “master connection”. Said primary connection is set up starting from the first communication unit via at least one node unit to the second communication unit, with addressing data being contained in the message addressing data used for setting up the primary connection and belonging to the communication units and node units involved in the primary connection and said addressing data being transmitted by means of control messages for setting up the primary connection. The primary connection is set up by the first communication unit via at least one node unit to the second communication unit, the number of node units included for the primary connection being dependent on the network structure. An entry node is registered with the aid of the transmitted addressing data of the communication unit involved in the setting up of the primary connection. The entry node is defined by the first conversion of circuit-switched to packet-oriented communication data necessary along the primary connection. The exit node is defined by the last conversion of packet-oriented to circuit-switched communication data necessary along the primary connection.
In this scheme the entry node is the first unit having valid addressing data, i.e. the first communication unit having valid addressing data itself or the first node unit having valid addressing data. In other words, in the event that the first communication unit has valid addressing data, said communication unit will be registered as the entry node. Valid addressing data in this case is for example the provision of a communication unit or node unit having a network address by means of which the communication unit or node unit can be addressed by a, for example, packet-oriented network. In an analogous manner a last node unit having valid addressing data and disposed along the primary connection or the second communication unit itself, provided it has valid addressing data, is registered as the exit node. Both, the entry node and the exit node, form the end nodes of a direct media connection that is to be embodied. Provided as the final method step is the embodiment of a secondary connection or direct media connection (DMC) between the formerly registered end node, i.e. entry node and exit node, via a network that is available in the communication system. The communication data, in particular payload data, is thereupon transmitted via the secondary connection. In the case of a choice of a packet-oriented transmission mode for the secondary connection this means that multiple conversions over the length of the secondary connection can be avoided. The packet-oriented transmission mode is retained without further conversion along the secondary connection as far as the exit node.
In short, the method for direct media connection is therefore characterized in that from the time of a connection being accepted by the called communication unit a direct connection via as large a segment of a common packet-oriented network as possible is embodied between two end points. In a transmission of communication data, in the form of voice for example, a substantial improvement in the voice quality is noticeable, both at the calling first and at the called second communication unit, as a result of the use of the proposed method.